The environment performs three basic functions in relation to man. First, it provides living space and other amenities that make life qualitatively rich for man. Second, the environment is a source of agricultural, mineral, water and other resources that are consumed directly. Third, the environment is a sink where all the waste produced by man is assimilated. Hydrogen Sulphide is produced by microbial decay of sulphur compounds and microbial reduction of sulphate, from geothermal steam, from wood pulping and from a number of miscellaneous natural and anthropogenic sources. Most atmospheric hydrogen sulphide is rapidly converted to SO2 and to sulphates. The organic horologes of hydrogen sulphide, the mercaptants, enter the atmosphere from decaying organic matter and have particularly objectionable odors.
[...] HYDROGEN SULPHIDE REMOVAL The feedstock for the production of synthesis gas consists of naphtha, fuel oil and coke. As almost all feed stocks contain some quantity sulphur, synthesis gas contains H2S which is recovered and generally burnt. The SO2 obtained the combustion of H2S can be converted to sulphuric acid where sulphuric plants exist. Alternatively H2S can be converted by the Claus process. H2S is one of the major air pollutants from petroleum industries. There are two modes of H2S removal from the petroleum industry 1. [...]
[...] Ethyl amine process Fig Absorption of H2S from effluent gas using ethyl amine In this process an aqueous solution of MEA, DEA or TEA is used for the absorption of H2S, CO2 and other acidic pollutants in the gases, with continuous regeneration of the absorbing medium and the solutes. The absorption efficiency for the gases is high at lower temperatures and, therefore, the gases should be cooled and made free of particulate matter before absorption. The temperature of the rich solution is raised (about 1000c) in a stripping column for recovery of solutes. [...]
[...] Process: HF membrane based gas/liquid absorption Contaminant - hydrogen sulphide Absorbent - dilute caustic solution Fig Removal of H2S from effluent gases using membrane contactor In this configuration, the hydrophobic membrane pores are gas filled, with liquid prevented from entering the membrane. To maintain this mode, the gas pressure, Pg, has to be higher than that of the liquid to prevent the latter from dispersing as drops into the gas phase (Figure 2). The gas liquid interface is at the pore mouth of the hydrophobic membrane on the liquid side, with the diffusion of gas occurring firstly, through the gas film in the pores, and finally dissolving into the contact liquid absorbent. [...]
[...] In a modified combustion process, called the double stream process, part of the gas stream containing H2S is completely burnt and the products of combustion or reacted with the rest of the gas, catalytically along lines similar to the partial combustion process. This process is also widely practiced in the non-regenerative process the gases are reacted with strong alkalis when H2S can be completely removed. This process is suitable only when the concentration of H2S in the tale gases is low and cost of regeneration is incompatible with the cost of chemicals used. [...]
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